Hi Matthew,
You've actually already got the answer: Off is 80-100v. Unlike LED's,
Nixies change state from a very high impedance device (below the
ignition/striking voltage) until the ignition voltage is achieved, where
they become very low impedance. The nixie will stay very low impedance
while "lit", until the voltage is dropped to below the "extinguishing"
voltage. Once the extinguishing voltage is achieved, the nixie goes back
to being a very high impedance device. Therefore, we do not need to sink
the entire 180v to turn the nixie off.
With clever application, there are tons of IC's that can be press-ganged
into driving nixie tubes. In fact, the venerable 74141 sinks only
something like 80v (I think).
VFD's aren't too hard to drive. If you look back through the list
archive, you will find lots of discussion on how to drive VFD's. The
easiest way for discrete tubes like the IV-4 is to run the filament on
DC off of a 5v supply (a beefy one, I like the simple-switcher series
because they can attach a heatsink). Run the segment voltage from a
small boost mode switcher, any nixie supply can probably be modified to
lower the output voltage into the correct range.
-Adam W7QI
On 6/7/2012 3:08 AM, Matthew wrote:
Adam, thanks for the reply, much appreciated.
As to driving the nixies, I feel I'm missing something - David
suggested the SN75468 transistor array, which I have seen mention of
elsewhere in reference to Nixies - but its rated at 100v, less than
that required by the tubes. Implying that the 'off' cathodes need to
be held at eg 80-100v somehow, rather than 0v? If so, is that just an
issue of this particular driver; or the 'right' way to drive them
whichever transistors are used?
Interesting you mentioned the VFD tubes - I'm now getting ahead of
myself and thinking of making a few of these (having seen the variable
vulgarity and bonus 8-letter expletives, everyone wants one...), so am
looking for other display alternatives and have just ordered some
IV-4s, which I see a couple of other folks have also made FLWs from
(although am as yet clueless as to how to generate the required voltage).
Any other ideas for readily-available display solutions? I'd love to
make a split-flap version, but they certainly don't seem
readily-available :|
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